The near-field microscope provided with an optical probe utilizing near-field light allows for sample observation with resolution exceeding beyond a diffraction limit of light. Such a near-field microscope has an optical probe using, at a sample-opposed end, a microscopic aperture provided at a sharpened tip of an optical fiber or in an on-silicon-substrate chip formed through anisotropic etching, or otherwise a sharpened tip of an optical fiber or a microscopic protrusion on that chip.
Meanwhile, there is a proposal of a near-field optical memory as disclosed, for example, in (E. Betzig et al., Science 257, 189 (1992)) applied with the above observation principle.
In such applications, there is a need to bring a microscopic aperture or protrusion formed in a recording or reading head into proximity to or contact with a recording medium surface, with a distance of less than a wavelength of an illumination light given as a propagation light.
The proposals on mechanisms for bringing into proximity the head and recording medium include a disclosure, for example, in (44th Applied Physics Related Association Lecture Thesis 28p-ZG-3) wherein a recording medium is rotated to cause a head having a microscopic aperture formed in a silicon substrate through anisotropic etching to float over an air film pushed through between the head and the recording medium as in a flying head used in a hard disk drive, thereby bringing into proximity the head and the recording medium.
However, in the usual flying head system as above, the air film pushed between the head and the recording medium is thick, i.e. the distance between a head bottom surface and a recording medium surface is several tens to several hundred nano-meters. This is too great to realize recording/reading utilizing a near-field light with high resolution and efficiency. In such a case, the near-field light has an intensity abruptly decreasing in an exponential fashion as gone distant from the microscopic aperture. Due to this, there has been a problem that, because the head and recording medium are positioned distant, the near-field light is low in intensity and hence a sufficient signal intensity is not obtainable. Furthermore, high resolution is difficult to realize.
Moreover, the distance between a light emitting element or light detecting element placed on a head top surface and a microscopic aperture in a head bottom surface is provided equal to a thickness of a slider. In the case of using a light emitting element, the intensity of light illuminating the microscopic aperture attenuates proportional to a square of the distance, resulting in a problem of difficulty in obtaining a sufficient signal intensity. In the case of using a light detecting element, there encounters a problem that no sufficient signal intensity is obtainable unless the light detecting section is made in a large area.
Meanwhile, during standstill of a head, the slider at its surface is contacted with a recording medium. Consequently, adsorption between the slider and the recording medium is enhanced by an adsorption water present on a recording medium surface, leading to a problem of damaging the slider and recording medium at a start of head operation. In order to avoid such a problem, conventionally a mechanism has been needed to move the slider in a direction vertical to the recording medium. This, however, results in a problem of drawback in reducing the head size.
Also, when floating the head, the slider is structurally inclined relative to the recording medium surface. Due to this, the microscopic aperture has to be arranged with tilt relative to the recording medium surface so that the microscopic aperture at one part is positioned distant from the recording medium. Because the intensity of near-field light attenuates in an exponential fashion against a distance between the microscopic aperture and the recording medium, it is difficult for the portion of the microscopic aperture that is distant from the recording medium to have sufficient interaction with the recording medium. Thus, there has been a problem of difficulty in obtaining a sufficient signal intensity.
Therefore, the present invention has been made in view of the above and it is an object of the present invention to provide a high sensitive, high resolving near-field optical head which is simple in structure with a reduced distance between a recording medium and a head, wherein control is made for a distance between the recording medium and the head to decrease a contact area of a slider with the recording medium at start and stop of operation and to put the probe out of contact with a recording medium during standstill, thus preventing damage to the probe and recording medium.